What is bed expansion?
Bed expansion in media filters is defined as the level of increase in the volume of filter media. There is a resting or a working bed depth and an expanded bed depth. This is the level to which the media needs to rise to during upflow or backwash.
- Filter Sand
- Ion Exchange Resins
- Granular Activated Carbon
- Greensand and others
- Ensure the diameter of the filter does not exceed the available pump capacity. Not enough volume = not enough velocity which = insufficient bed expansion.
- The cylindrical wall height of the vessel is calculated correctly. If the cylinder height is not high enough it means that the media has no room to expand and it will be discharged out the waste line when backwashing.
- If the expanded bed height is 1500mm, then you must have a filter vessel with a 1500mm cylindrical wall height.